Composite Catalyst Preparation And Its Performance For Air-cathode Microbial Fuel Cells

Microbial fuel cell(MFC) technology achieve the direct conversion from biomass energy to electrical energy. While air cathode microbial fuel cells is more likely to be applied on a large scale. The kinetics of oxygen reduction of cathode catalyst and the price of materials of air cathode are critical factors that limit the electricity production efficiency of microbial fuel cells. This study focuses on the composite catalyst preparation method and its impacts on the performance of the air cathode. On the basis, the materials and production methods of the air cathode were further optimized to reduce costs while kept the performance of air cathode MFC maintaining a higher level.The composite catalysts of MnO2 and activated carbon was prepared with two different methods, namely mechanical mixing and chemical composite. And the composite catalysts ratio(MnO2: supercapacitor activated carbon) was 1:3, 1:1 and 3:1, respectively. The production were tested by X-ray diffraction(XRD), energy dispersive X-Ray Spectroscopy(EDX), scanning electron microscopy(SEM), and BET surface area and pore size distribution method to characterize the catalysts. Then applying linear sweep voltammetry(LSV) method and electrochemical impedance spectroscopy(EIS) method on the air cathodes in different proportions of composite catalysts for electrochemical performance analysis. Finally, air cathode was used in MFC, exploring the performance of air-cathode MFC.It is shown that both composite pattern and ratio of the catalyst have great influences on air cathode. The maximum power density of MFC with chemical composite catalyst is 336 mW/m2, which is larger than that of mechanical mixing catalyst(312.5 mW/m2). The best ratios of the two kinds of catalysts are the same 1:1 when they reach the maximum power density. Under the conditions of the three composite proportions, chemical composite catalysts achieve better performance. Meanwhile, the maximum output power of the composite catalyst is more than twice the performance of MFC with MnO2 powder or activated carbon. The catalytic performance of the composite catalysts realizes obviously improved. Lower cost of the composite catalyst makes it a feasible catalyst solution.Optimization of the air cathode with materials and preparation process include: simplifying method of catalyst preparation, reacting KMnO4 with supercapacitor activated carbon directly; a lower price of the cathode material, nickel foam as current collector, PTFE as binder, and the diffusion layers are made of PDMS; reducing cathode production steps, the catalyst layer is rolled on the nickel foam, and PDMS coated with two layers only. Operating results of the optimized air cathodes MFC show that when the feeding ratio of KMnO4: AC is 1:3, the maximum power density was 321.2mW/m2, which is increased by about 20% over the activated carbon MFC. However, with the increase of the content of the MnO2, the maximum power density is gradually decreased. When the composite catalyst controlled in a certain mass ratio, air-cathode MFC could generate high power output. It would enlarge the application range of air cathode MFC.